1. Field of the Invention
The present invention relates to a method of cleaning a thermal head of a thermal printer. More particularly, the present invention relates to a method of cleaning a thermal head with great ease.
2. Description Related to the Prior Art
There are thermal transfer printers and direct thermal printers known in the art. The thermal transfer printers are classified into a thermal die sublimation transfer type and a thermal wax transfer type. The direct thermal printing is featured by low costs in operation and no creation of waste with heating of the thermosensitive material. In a direct thermal printer, a thermosensitive recording sheet is set on a periphery of a platen drum, which is rotated to move the recording sheet in a main scanning direction. During the movement of the recording sheet, a front edge of an area effective for the recording comes to lie under a thermal head. In response to this, the thermal head is swung or shifted toward the platen drum to press the recording sheet. A great number of heating elements, arranged linearly to constitute the thermal head, is driven to generate heat energy in correspondence to image data, and forms an image to the recording sheet in the effective area line after line. As soon as a rear edge of the effective area come to lie under the thermal head, the thermal head is shifted away from the recording sheet.
There is also a known color thermal printer which is used with a color thermosensitive recording sheet including a support and cyan, magenta and yellow thermosensitive coloring layers laid on the support. The thermal printer has a platen drum, which is driven to make three rotations to record the three primary colors by coloring the coloring layers in an order toward the support. In the color thermal printer, the yellow coloring layer, having received heat energy first for producing yellow color, is provided with application of ultraviolet rays peaking at a wavelength of 420 nm, for fixation of the yellow coloring layer in avoidance of receiving influence of further heat energy for the remaining coloring layer. The magenta coloring layer, having received heat energy secondly, is provided with ultraviolet rays peaking at a wavelength of 365 nm for fixation of the magenta color.
The thermal head presses the recording sheet while printing an image. It is very likely with time that the thermal head is provided with dust stuck on recording sheets, or dust derived from scratching or rubbing a protective layer on an obverse face of the recording sheet, for example dust of lubricant agent in the protective layer. The thermal head is highly susceptible to dust, dirt or other deposits.
When dust or other deposit is stuck on the thermal head, an image printed through the thermal head is degraded remarkably, because the ability of the thermal head to transmit heat is lowered. If the whole of the thermal head is coated with dust, then the density of the printed image may be lowered. If the thermal head is partially coated with dust, then the printed image may include white stripes. If the dust on the thermal head is hardened with time, then the dust may scratch recording sheets in contact. The thermal head, in the course of long use in the thermal printer, requires cleaning.
Conventionally, it is highly difficult to clean the thermal head, because the thermal printer must be disassembled to remove the thermal head. A cover of the thermal printer must be dismounted before the thermal head could be removed from a chassis of the printer.